Pre-term birth accounts for about 6-8% of all pregnancies and is responsible for 75% of all perinatal deaths. Currently, pre-term birth can be delayed for a few days by administering a muscle relaxing agent which serves to relax the myometrium. However, there is a need for agents which can delay the onset of labour for longer periods to avoid children being born very prematurely. Additionally, many full term deliveries are made difficult because, whilst there is strong myometrial activity, there is insufficient cervical ripening. Thus, there is a need to be able to control cervical ripening in a similar way to that in which myometrial activity can be controlled so that further control over pre-term and difficult full- or post-term deliveries can be exercised.
The present invention has been made as a result of investigation of the mechanism which leads to ripening of the cervix during pregnancy. The cervix has commonly been regarded as serving a purely passive role in which it softens or ripens during pregnancy to facilitate passage of the foetus during delivery. It is known that prostaglandins and oestrogen have a part to play in the changes in cervical properties which take place during pregnancy, but the mechanism by which they act is poorly understood.